The potential hazards of waste disposal have, in recent years, captured the attention of industry, government, and the public. The growth of the chemical processing and power generating industries, in particular, has resulted in the production of a large number of by-product materials (e.g., waste products) which are potentially hazardous to man and his environment. Recognition of these hazards is exemplified by the passage of the Resource Conservation and Recovery Act (RCRA) of 1976, the increased attention applied to the disposal of radioactive wastes, and a variety of legislation and regulations aimed at protecting the environment from such hazards.
The necessity for these legislations and regulations was in large part due to inadequate protection of the environment with respect to waste disposal. Accordingly, it is believed that new methods of waste disposal will be required to meet these new, more stringent regulations.
The basic objective of the present invention is to provide a process which can reduce the volume of powdered waste and immobilize hazardous wastes in a solid form. It is a further object of the present invention to render the processed waste product resistant to thermal, mechanical and chemical attack mechanisms which might be expected during transporting, storage, or disposal in a hydrogeological environment.
Various methods have been suggested and developed for solidifying waste material such as low level radioactive waste materials including solidification with a bonding agent such as cement, borosilicate glasses, urea-formaldehyde resins, and bitumen. In addition, it has recently been suggested to treat nuclear waste by admixing the waste with a ceramic material and then sintering by hot isostatic pressing process (along these lines see Metal Powder Report, Volume 32, No. 3, March 1977, pages 98 and 99, and "Technologies for the Recovery of Transuranium Elements and Immobilization of Non-High-Level Wastes," G. L. Richardson, pages 307-313, Proceedings of the International Symposium on the Management of Wastes from the LWR Fuel Cycle, July 11-16, 1976, Denver, Colo., sponsored by ERDA).
This latter publication also suggests a process employing cold pressing and requiring a heat treatment after pressing to effect sintering. The sintering temperature is about 1000.degree. C. On the other hand, the present invention does not require such sintering and still achieves strong solid products. This is believed to be due at least in part to the fact that this prior process suggested requires a ceramic rather than the types of metal employed herein. The "metal matrix" mentioned in FIG. 28 on page 309 of said article refers to the metal surface coating used in the "inertification" step suggested in said article.
Additional prior art which is of general interest concerning this subject matter includes U.S. Pat. Nos. 3,213,031 and 4,028,265 which suggest adding various materials to waste products and heating the mixture. In addition, U.S. Pat. No. 3,994,822 suggests coating waste particles with an alpha-silicon carbide, then heating to carbonize the binder. This patent also suggests hot pressing in order to melt silicon and carbonize the carbide in order to enclose the waste material.
Moreover, U.S. Pat. Nos. 3,993,579 and 4,010,108 are representative of those disclosures which suggest employing synthetic resins in treatment of waste material. U.S. Pat. No. 3,865,576 is of interest in that it suggests preparing a nuclear fuel by mixing UO.sub.2 -BeO and then hot pressing the mixture.